This paper investigates the spectral radius and energy of the atom-bond sum-connectivity (ABS) matrix. Through rigorous mathematical analysis, we establish bounds for the ABS spectral radius across several graph classes and investigate its properties. The ABS energy is defined, and its calculation methods and properties are studied. Furthermore, by analyzing the correlation between the ABS spectral radius and the physicochemical properties of octane isomers, it is revealed that the ABS spectral radius performs well in predicting molecular properties, indicating its potential application value in chemical structure-property modeling.